In this photo taken May 27, 2015, Golden State Warriors guard Klay Thompson, bottom, is checked on by teammates after taking a knee to his head from Houston Rockets forward Trevor Ariza during the second half of Game 5 of the NBA basketball Western Conference finals. The Warriors hope to get healthy and stay in tune over the next week before facing the Cleveland Cavaliers in the NBA Finals. Thompson needs to pass through the league's concussion protocol and Stepehen Curry is trying to get his aching body back at full strength. (AP Photo/Tony Avelar, File

In this photo taken May 27, 2015, Golden State Warriors guard Klay Thompson, bottom, is checked on by teammates after taking a knee to his head from Houston Rockets forward Trevor Ariza during the second half

In this photo taken May 27, 2015, Golden State Warriors guard Klay Thompson (11) reacts after taking a knee to his head from Houston Rockets forward Trevor Ariza (1) during the second half of Game 5 of the NBA basketball Western Conference finals. The Warriors hope to get healthy and stay in tune over the next week before facing the Cleveland Cavaliers in the NBA Finals. Thompson needs to pass through the league's concussion protocol and Stepehen Curry is trying to get his aching body back at full strength. (AP Photo/Tony Avelar)

In this photo taken May 27, 2015, Golden State Warriors guard Klay Thompson (11) reacts after taking a knee to his head from Houston Rockets forward Trevor Ariza (1) during the second half of Game 5 of the NBA

In this photo taken May 27, 2015, Golden State Warriors guard Klay Thompson reacts after taking a knee to his head from Houston Rockets forward Trevor Ariza during the second half of Game 5 of the NBA basketball Western Conference finals. The Warriors hope to get healthy and stay in tune over the next week before facing the Cleveland Cavaliers in the NBA Finals. Thompson needs to pass through the league's concussion protocol and Stepehen Curry is trying to get his aching body back at full strength. (AP Photo/Ben Margot)

OAKLAND, Calif. (AP) -- The initial hit caused Klay Thompson plenty of pain. The final diagnosis delivered another blow to him and the Golden State Warriors as they prepare for the NBA Finals.

Two days after he got kneed in the head by Houston's Trevor Ariza, the Warriors said Friday that Thompson has a concussion and will not return to practice until he is symptom free.

The All-Star guard went through neurological tests that confirmed the concussion. He was injured in the fourth quarter of Golden State's 104-90 win over the Rockets in the Western Conference finals clincher Wednesday night.

The NBA Finals start Thursday against Cleveland. And while the Warriors are optimistic Thompson will be cleared before then, he must pass through the league's concussion protocol first.

"This break has turned out to be good for us," Warriors coach Steve Kerr said after Friday's practice. "And maybe good for Cleveland, too, because they've got some injuries. It's just something we've got to work through and we'll see how it goes."

Cavaliers guard Kyrie Irving has been slowed by knee tendinitis and a sore foot, and four-time NBA MVP LeBron James has been banged up as well.

But neither of those injuries seems as serious as the one the Warriors are facing now.

Thompson was at the team's facility Friday but did not participate in the workout. The Warriors will practice again Saturday and take Sunday off.

Kerr said he's not concerned about Thompson staying sharp.

"Klay picks up his rhythm very quickly," Kerr said.

It's unclear how long Thompson could be away from the court -- and that's the concern for the Warriors.

The NBA's concussion policy requires players to pass a series of steps without experiencing symptoms before they can return. That starts with riding a stationary bike and progresses to jogging, agility work and non-contact team drills, according to the league. Players must start over if they experience any symptoms.

The protocol also requires the team physician to discuss the process with Dr. Jeffrey Kutcher, the director of the NBA's concussion program, before a player can return.

Kerr insisted he will heed the advice of the medical staff as he always has with injuries.

"I just do what the doctors say we should do," Kerr said. "Obviously, we want to be as careful as possible and make sure our players are safe and sound and healthy. So we'll follow this protocol that the league provides and we'll have Klay out here when he's ready."

Team doctors initially cleared Thompson to return to the game. He ended up not playing, and the team said he started developing symptoms after the game, fueling questions about the league's concussion protocol.

Thompson's father, former NBA player Mychal Thompson, had to drive his son home after the game because he was feeling ill. He said Thursday that Klay vomited a couple of times but had been feeling "better by the hour" and was confident that doctors would clear him before the finals begin.

Thompson also needed stitches on his right ear after the hit caused blood to spill down the side of his head.

It was the second consecutive game the Warriors were under scrutiny for letting an All-Star player return after getting banged up.

Point guard and MVP Stephen Curry got hurt in the second quarter of Game 4 when he jumped as Ariza was about to go up for a shot. Ariza saw him and stopped abruptly, causing Curry to tumble over him. Curry's head and right arm hit the court, where he remained for several minutes.

Curry returned in the third quarter after passing the concussion protocol. He was diagnosed with a bruised head and a bruised right arm -- but has not shown any signs of a concussion, the team said.

Curry called it a strange coincidence and said he's confident in the system in place.

"The amount of times that that's happened, I don't think that's too prevalent in basketball," Curry said. "You kind of just go based on how you feel, the test that they run, and you have confidence that if they say you're OK to go out and play. But in the cases that I had, if you feel not yourself, you let them know and they pull you out and kind of reassess.

"That's why the protocol is what it is. You go through tests, if you pass, you're able to go back in there. You make a judgment call. Hopefully in basketball you don't put yourself in too much danger as in other sports where you might be taking those big hits."